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Date: Tue, 10 Aug 2004 15:01:22 +0200
From: Ingo Molnar <mingo@elte.hu>
To: William Lee Irwin III <wli@holomorphy.com>, V13 <v13@priest.com>,
       Jesse Barnes <jbarnes@engr.sgi.com>, Andrew Morton <akpm@osdl.org>,
       linux-kernel@vger.kernel.org, Nick Piggin <nickpiggin@yahoo.com.au>
Subject: Re: 2.6.8-rc3-mm2
Message-ID: <20040810130122.GA26326@elte.hu>
References: <200408091217.50786.jbarnes@engr.sgi.com> <20040810100234.GN11200@holomorphy.com> <20040810115307.GR11200@holomorphy.com> <200408101552.22501.v13@priest.com> <20040810125140.GU11200@holomorphy.com> <20040810125529.GA22650@elte.hu> <20040810125651.GV11200@holomorphy.com>
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* William Lee Irwin III <wli@holomorphy.com> wrote:

> On Tue, Aug 10, 2004 at 02:55:29PM +0200, Ingo Molnar wrote:
> > i'd guess it's the con->write() in __call_console_drivers() that makes
> > the difference. (i.e. touching the framebuffer)
> 
> This is serial port IO; would that make the same kind of difference?

serial port IO is even more heavy, it also generates IRQ traffic. I'd
suggest the following tests: modified kernel without serial console, and
original kernel without serial console. This way you can find out 
whether the hang itself is triggered by the serial console.

another attack angle is to find out what state the system has during the
hang. Is it debuggable?

	Ingo